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RF coil - RF Cafe Forums

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 Post subject: RF coil
Posted: Wed Jul 13, 2005 8:06 am 
 
Lieutenant

Joined: Wed Jul 13, 2005 8:01 am
Posts: 1
Hi everyone, im new to this group so i hope you can help me...
I've been working with HFSS for a while now, designing RF coils for MRI. The structure is pretty simple - a single turn coil with a coax feed. the feed is blocked by a copper block on its port end, and the inner coax connects to the coil... (coil radius=7cm) the problem is that i keep getting negative real part for my impedance in low freq. (around 100MHz).
Happend to any of you? what's that supposed to mean in HFSS?

thanks in advance
Alex


 
   
 
 Post subject:
Posted: Tue Jul 19, 2005 7:26 pm 
 
Site Admin
User avatar

Joined: Sun Aug 03, 2003 2:02 pm
Posts: 308
Location: Erie, PA
Greetings Lechko:

I am not a HFSS user, but negative impedances in other simulators often indicate you are sampling at physical point that is located at or near a peak in a standing wave on the line. Constructive interference there can create a voltage greater than that which is applied. This is an indication of an impedance mismatch at the sampled frequency.

Or, it could be something else :lol:


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